Introduction to Infectious Agents & Bacterial structure Flashcards by martin camaj

What are some infectious agents?

Bacteria: prokaryotes (unicellular)
viruses: acellular
fungi: eukaryotes (uni/multicellular)
parasites: eukaryote
(unicellular [protozoan]multicellular[metazoan])

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What % of known bacteria are non-pathogens?

95%

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What % of all known bacteria cause human diseases?

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under normal circumstances are harmless & may be beneficial

Normal flora - also known as commensals(non-pathogens)

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Normal flora compete for nutrients w/ pathogens, produce antimicrobial substances, & immune system stimulus in the newborn. Also, does 2 other things?

provide nutrients & block host receptors for pathogens

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What are some true pathogens able to cause disease?

Ebola and plague (Yersinia pestis)

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This pathogen causes disease when: immunocompromised, normal flora introduced into inappropriate body cavity, & overgrowth of normal flora?

Opportunistic pathogens

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Classification of infectious disease by duration:

develops & runs its course quickly?
develops more slowly * is usually less sever, but may persist for a long, indefinite period of time?
characterized by periods of no symptoms between outbreaks of illness?

acute.
chronic.
latent.

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Classification of infectious disease by location:

confined to a specific area of the body?
a generalized illness that infects most of the body w/ pathogens distributed widely in tissues?

local.

systemic.

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Classification of infectious disease by timing:

initial infection in a previously healthy person?
infection that occurs in a person weakened by a primary infection?

primary.

secondary.

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Phases of infectious disease:

time between infection & the appearance of signs & symptoms?

Incubation period

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Phases of infectious disease:

mild, nonspecific symptoms that signal onset of some diseases?

Prodromal phase

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Phases of infectious disease:
a person experiences typical signs & symptoms of disease? (some individuals may be carriers of particular pathogens & not exhibit symptoms)

Clinical phase

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Time course of infectious disease:

Transmission, entry, _____, invasion, propagation, damage, & resolution

adherence

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Human to human transmission:

Horizontal:?
Vertical:?

Horizontal: direct contact
Vertical: mother to offspring

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Examples of non human to human transmission?

soil/water source,
animal,
fomites

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Adherence-Entry

external features: capsules, surface antigens, flagella, fimbriae
may use endocytosis for entry if there is an intracellular stage in life cycle

Bacteria & Fungi

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Adherence-Entry

external features: envelopes, peplomers, capsids
endocytosis or fusion to host cell for entry

Viruses

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Adherence-Entry

external features: surface antigens, mechanical attachment
may use endocytosis for entry if there is an intracellular stage in life cycle

Parasites

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Examples for portals of entry

mucus membranes,
skin,
parenteral

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Easiest and most frequently traveled portal of entry?

respiratory tract

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common diseases contracted via the respiratory tract?

common cold, flu, tuberculosis, whooping cough, pneumonia, measles, strep throat, diphtheria

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Microbes gain entrance through contaminated food & water or fingers & hands?

gastroinstestinal tract

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common disease contracted via the g.i. tract?

salmonellosis, shigellosis, cholera, ulcers, botulism

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When unbroken is an effective barrier for most microorganisms?

skin

some microbes can gain entrance through openings in the skin:?

hair follicles & sweat glands

Portal of entry where microorganisms are deposited into the tissues below the skin or mucus membranes or punctures, injections, bites, scratches, surgery, & splitting of skin?

Parenteral

Replication of some organisms may cause mechanical damage; direct destruction called cytopathology occurs due to?

viral replication

block physiological or metabolic processes?

Exotoxins(secreted)

Shapes of bacteria?

cocci, bacilli-rods, spirochetes, pleomorphic

size range for bacteria?

0.2 to 5 um

The cell wall provide shape & helps cell maintain its integrity under?

changing environmental conditions

Bacteria are divided/classified based on their?

cell wall structure/biochemical makeup - gram +, gram -, acid fast - cell wall-less

Gram negative goes thru fixation->crystal violet -> iodine treatment -> decolorization -> ?

counter stain safranin | gram+ stops at iodine treatment

Staphylococcus aureus is what type of gram stain?

gram positive

Gram positive cell wall structure has a thick what?

peptidoglycan layer

E. coli (bacilli) is what type of gram stain?

gram negative

what will not be found in gram positive

lipopolysaccharide (LPS)

gram negative cell wall structures of LPS?

O-Antigen, Core polysaccharide, Lipid A

Used to identify organisms in the genus mycobacterium?

Acid-Fast stain

Acid-Fast or Non Acid-Fast: | uses carbol fuchsin then decolouriser then counterstain?

Non Acid-Fast (A)

Acid-Fast or Non Acid-Fast: | uses carbol fuchsin?

Acid-Fast (B)

Components: peptidoglycan with glycolipid polymers woven throughout

Acid Fast cell walls

Examples of Acid Fast Bacteria?

Mycobacterium

Components: NO peptidoglycan. STEROLS w/in a phospholipid bilayer membrane: Maintain fluidity.

Cell Wall-Less Bacteria

Examples of Cell Wall-Less Bacteria?

Mycoplasma

Bacteria's plasma/cell membrane is a phospholipid bilayer that is a site of transport & site of ATP production. The outer membrane has? The inner membrane has?

Outer: Porins Inner: Permeases

External structure of bacteria that are used for motility. Highly conserved. Capable of being regenerated. Found on many but not all bacteria.

Flagella

External structure of bacteria only found in Spirochetes

Axial Filaments or endo-flagella

Function: adhesion to host cell surface. Virulence factor. Cell communication.

Pilus & Fimbria

adhesion & transport of bacterial proteins or DNA -conjugation

Sex pili

Sex pili are mainly on gram ____ bacteria

negative

Glycocalyx-slime layer: surround single cells and provide: adhesion & protection

Capsules

Capsules provide protection against?

Phagocytosis Dehydration Antibiotic penetration

What are capsules composed of?

Mucopolysaccharides Polypeptides (poorly immunogenic)

Living layers- microbes undisturbed cling on surfaces/organic materials. As they grow, they provide adhesion & protection (like capsule)

Biofilms

What is the composition of biofilms?

Mucopolysaccharides

Bacteria internal structures has genetic material & ribosomes. What are some genetic material examples?

Chromosome Pathogenicity islands Plasmids

Extra-chromosomal genetic elements- drug resistance. Non-essential genetic information.

Plasmids

Some types of Granules?

- Glycogen - Lipids - Poluphosphates

Survival forms (not reproductive). Not metabolically active. Formed in response to adverse conditions.

Endospores

Endospores ___ contains high concentration of calcium bound to dipicolinic acid, plus a keratin-like protein

core

Bacteria uptake material by 3 main pathways

Facilitated diffusion Active transport Group translocation

Secretion systems (Types I-VI) used for secretion/transport in gram ____ bacteria

negative

Some types of bacterial products?

Exoenzymes Exotoxins Endotoxins

Used to facilitate invasion of the host. | Ex: Lipases, Proteases, Hyaluronidase, Hemolysins, DNases

Exoenzymes

Proteins secreted by many bacteria. Produced by both gram + & gram -

Exotoxins

Exotoxins in gram negatives are secreted via what?

Type I-VI transport systems

What are the 3 main types of exotoxins?

1. A-B Toxin- never secreted via Type III system 2. Membrane-Disrupting Toxins 3. Superantigens

__ subunit binds host cell receptor. Determines the host cell specificity of the toxin

B subunit toxin

__ subunit mediates the enzymatic activity responsible for toxicity

A subunit toxin

Antibodies against B subunit prevent what?

toxin activity

Can be classified as hydrolytic products | -some called lysins

Membrane Disrupting Toxins

Superantigens form bridges between the MHC class II off what?

APCs & TCRs on T cells

High levels of ____ in circulation can cause nausea, vomiting, malaise, & fever

cytokines

Structural component of the bacteria?

Endotoxins (Lipid A component of LPS)

Lysis may be due to MAC formation, phagocytosis after complement opsonization, or ______

antibiotics

High concentration of the Lipid A component of LPS may result in?

Endotoxic shock

Property: - Chemical Nature: Lipopolysaccharide - Relationship to cell: Part of outer membrane - Antigenic: Yes, poorly - Can form toxoid?: No - Specificity of Ab: Low

Endotoxin

Property: - Chemical Nature: Protein - Relationship to cell: Extracellular, diffusible - Antigenic: Yes - Can form Toxoid?; Yes - Specificity of Ab: High

Exotoxin

Bacterial growth process?

asexual reproduction-binary fission

Bacterial growth measurement?

Direct: microscopy Indirect: plate (CFU)